Curtain dampers



Aug. 15, 1961 E. LOWE 2,996,063

CURTAIN DAMPERS Filed June 23, 1960 2 Sheets-Sheet 1 Aug. 15, 1961 E. LOWE 2,996,063

CURTAIN DAMPERS Filed June 23, 1960 2 Sheets -Sheet 2 United States Patent C 2,996,063 CURTAIN DAMPERS Ernest Lowe, London, England, assignor to Amereng This invention relates to dampers for providing a gastight seal in flues or other ducts through which flow gases and is a continuation-in-part of application Serial No. 615,912, new Patent 2,964,036.

Various types of dampers have been used for this purpose. Thus a louvre damper is described in British Patent No. 731,252 which has leaf-spring sealing elements. Such a damper, Whilst it gives a satisfactory seal for small or medium sized flues for boilers and furnaces, can be used only with rather limited spindle lengths and is therefore unsuitable for flues of large cross-section. Another disadvantage of the louvre damper is that it constitutes a permanent obstruction in the flue and when the gas Velocities are high this causes a pressure drop and is also subject to erosion.

For the gas-tight sealing of fines of large cross-section curtain dampers have been used (see for example British Patent No. 453,477) which comprise a frame and a curtain mounted at one side of the frame and adapted to be drawn across the frame to close it. Such dampers as hitherto proposed have provided only an aerostatic seal. If the static diiferent-ial of gas pressure is too small it may then be insufilcient to overcome creases and uneveness in the curtain materials and hence a poor seal will result.

Also the aerostatic seal only works for one direction of gas flow and is destroyed if the gas flow reverses its direction or is pulsating.

.With the type of curtain material hitherto proposed, i.e. asbestos or similar heat-resisting fabric, destruction of the curtain can result either by bagging out of the material between supporting grid bars if the pressure diiferential is too great, resulting in permanent distortion of the material, or by. vibration caused by a pulsating gas flow.

Furthermore, this type of material even in the thickest weaves is permeable and leakages result which in some circumstances may not be tolerable. Increasing the thickness of the material will reduce its flexibility which will adversely affect the seal.

I have found that substitution of thin sheet metal for the heat-resisting fabric in the aerostatic curtain damper is not satisfactory. Thus distortion between the grid bars and corners soon gives a permanent set which spoils the seal.

It is an object of the invention to provide a curtaintype damper which overcomes the above mentioned difliculties.

. The invention consists of a curtain damper comprising a frame, a gas-impermeable curtain, means for mounting the curtain to one side of the frame, means for drawing the curtain across the frame to a closed position, and means for effecting a seal between the margins of the curtain extending in the direction of movement and the frame in the closed position comprising strips of sheet material extending along the margins, flexible along their length and resiliently flexible across their width, and arranged to be resiliently flexed across their width in the closed position of the curtain to eifect the seal.

The curtain may be rigid and slid bodily across the frame and back out of the frame or it may be flexible and slid bodily or rolled and unrolled.

It may be mounted above the top side, below the bottom side, or to one or other lateral sides of the frame.

The marginal strips are secured to the frame. Two or more sets of marginal strips may be provided to seal the same marginal edge.

The marginal strips may be permanently held in their resiliently flexed position or the bending may be effected (or increased) as the curtain is slid or rolled into the closed position.

In the latter case the flexibility along the length of the strips enables them to follow the movement of the curtain, while in general it enables the strips to adapt themselves to any warpage which may occur.

Generally it will be desirable to have the strips resiliently flexible along their length also and to this end the strips may be of sheet metal alloy having spring temper and suitable resistance against heat and corrosion, such as heat-resisting steel, Monel 'or other nickel alloys and titanium sheet.

Conveniently the whole width of the curtain may be of such sheet metal which then provides margins of the de-' sired properties.

Alternatively, the spring temper marginal strips may be secured also to a curtain or press on to a curtain made from quite diflerent material such as light metal alloy or copper-nickel alloy.

Such a curtain may be stifiened with spaced parallel bars secured thereto (at right angles to the direction of movement in the case of a rolled curtain) and these may be supported by spaced parallel bars across the frame at right angles to the curtain bars.

Alternatively, the curtain may be of asbestos faced on one or both sides with sheet steel.

Considering now the arrangement for resiliently flexing or maintaining resiliently flexed the marginal strips in the closed position of the damper, various possibilities arise.

If one set of marginal strips is used then it is possible to have the curtain held against a marginal abutment on the frame at the same time flexing the marginal strips; The strips may be secured to the frame and flexed against thencurtain and, if desired, against another abutment as we This method gives an efficient seal for either direction of gas flow.

If two sets of marginal strips are used these may be secured to the frame and resiliently flexed oneon each side of the curtain. i

These arrangements would also provide a seal for either direction of gas flow.

The arrangements for sealing the leading edge of the curtain extending at right angles to the direction of movement as the curtain is closed may be similar in construction to those for sealing the edges of the curtain extending in'the direction of movement. Conveniently, one or both edges of the curtain extending at right angles to the direction of movement may be sealed by marginal strips of heat-resistant, spring steel sheet secured to the frame on one side of the curtain and resting against the curtain over a flat portion of the strips.

The curtain may be pushed (if suitably constructed) or pulled to draw it across the frame and various means of operation may be used.

Flue dust ejection arrangements may be provided if desired.

The invention will be further described with reference to the embodiments shown in the accompanying drawings.

FIGURE 1 is a vertical section of a roller curtain damper in accordance with the invention on the line II of FIGURE 3. 7

FIGURE 2 is a section on the line IIII of FIGURE 1.

FIGURE 3 is a section on the line III-III of FIG;

URE 1. a

FIGURE 4 is a detail corresponding to FIGURE 2 of an alternative form.

In FIGURES 1 to 3, the frame 1 is adapted to be closed by a heat-resistant sheet-steel curtain 2 having marginal leaf-spring strips 2a. The curtain is guided into position by bars 3 across the frame, three on one side and two on the other.

To raise the curtain, it is rolled at the top through headgear casing 4 and around a roller (not shown). The roller is operated from an electric motor mounted on the headgear or may be operated by hand in an emergency.

At the top the curtain emerges into the frame over a top seal comprising strips of spring steel heat-resistant sheet mounted in the head-gear 4, one on each side of the curtain, and adapted to bear against the curtain from the respective sides over a flat portion of the steel strip.

The strips are bent back at the edges in a permanent set to allow the curtain to slide into the headgear without catching in the edges of the strips.

To lower the curtain, rope 3 attached to the bottom of the curtain at each corner and extending over pulleys 9 and 9' is driven by suitable means (not shown).

At the bottom, two strips 11 of leaf-spring are provided and these are flexed to bear one on each side of the curtain 2.

Two heat-resistant spring steel strips 14 are provided; these being secured to abutment member 12 on the frame 1 by strips 13 and form part of the frame, bearing one on each side of the marginal strip 2a of the curtain 2 under an acute angle.

. This will provide arrangements suitable for sealing a flue in which the gas flow may be in either direction. For this purpose, the-frame 1 is installed in the flue, the imperforate curtain 2 forming alreciprocable damper in the frame. When the curtain is in its upper position, the flue gases may freely pass through the open frame 1, while in the indicated lower position of the curtain 2, the passage through the frame is closed. By the co-operation of the imperforate strips 14 and the marginal strips 2a of the curtain a gas-tight seal is obtained even under distorted conditions.

In FIGURE 4 the marginal strips 14 are shown as being attached in a slightly different manner to the frame '1 by means of the abutment member 12', strips 13 and screws 15 so that the marginal strips 14 are held fiat on the elongated planar surfaces 12a of the abutment 12 extending at acute angles to the frame, i.e. to the plane of the frame aperture.

I claim:

1. A flue sealing arrangement comprising an open frame for installation in a flue, a reciprocable curtain-type damper in said frame, a first co-operable imperforate wall means forming at least part of said damper, a second co-operable imperforate wall means forming part of said frame relative to which said first co-operable means is movable, means operatively connected to said first cooperable means for reciprocably moving the latter relative to the opening of said frame, said second co-operable means including abutment means having an elongated planar surface extending at an acute angle to said frame and supported thereby, said second co-operable means terminating in a marginal edge, said first co-operable means being movable between a first position allowing free passage of flue gases through said open frame and a second position closing said passage through said frame, said second co-operable means having heat-resistant marginal spring strip means secured to said planar surface and extending in planar form when non flexed and engaging said marginal edge of said first co-operable means, said strip means terminating in at least one free edge projecting beyond said marginal edge onto the surface of said first co-operable mean and in surface contact therewith so that inward and outward portions of said strip means are in contact engagement with said first cooperable means, said spring strip means conforming to the contour of said first co-operable mean even in distorted conditions and upon said free edge of said st-rip means 4 being pressed thereagainst in overlapping and surface contact relation due to the inherent resilient force of said strip means in said second position of said first co-operable means, to thereby form a gas-tight seal in said fiuc.

2. A flue sealing arrangement comprising an open frame for installation in a flue, a reciprocable curtaintype damper in said frame, a first co-operable imperforate wall means forming at least part of said damper, a second co-operable imperforate wall mean forming part of said frame relative to which said first co-operable means is movable, means operatively connected to said first co-operable means for reciprocably moving the latter relative to the opening of said frame, said second cooperable means terminating in a marginal edge, said first co-operable means being movable between a first position allowing free passage of flue gases through said open frame and a second position closing said passage through said frame, said second co-operable means having heatresistant marginal spring strip means secured thereto and extending in planar form when non-flexed at an acute angle to the plane of said first co-operable means and engaging said marginal edge of said first co-operable means, said strip means terminating at least in one free edge projecting beyond said marginal edge onto the surface of said first co-operable means and in surface contact therewith so that inward and outward portions of said strip means are in contact engagement with said first co-operable means, said spring strip means conforming to the contour of said first co-operable mean even in distorted conditions and upon said free edge of said strip means being pressed thereagainst in overlapping and sur face contact relation due to the inherent resilient force of said strip means in said second position of said first co-operable means, to thereby form a gas-tight seal in said flue.

3. A flue sealing arrangement comprising an open frame for installation in a flue, a reciprocable curtaintype damper in said frame, a first co-operable imperforate wall means forming at least part of said damper, a second co-operable imperforate wall mean forming part of said frame relative to which said first co-operable means is movable, means operatively connected to said first cooperable means for reciprocably moving the latter relative to the opening of said frame, said second co-operable means including abutment means having elongated planar surfaces extending at acute angles to said frame and supported thereby, said second co-operable means terminating in a marginal edge, said first co-operable means being movable between a first position allowing free passage of flue gases through said open frame and a second position closing said passage through said frame, said second cooperable means having two inwardly convergent heatresistant marginal spring strip means respectively secured to said planar surfaces and extending in planar form when non-flexed at an acute angle to the plane of said first cooperable means, one on each side thereof, and engaging said marginal edge of said first co-operable means, said strip means terminating in at least one free edge projecting beyond said marginal edge onto the surface of said first co-operable means and in surface contact therewith sothat inward and outward portions of said strip means are in contact engagement with said first co-operable means, said spring strip means conforming to the contour of said first cooperable means even in distorted conditions and upon said free edge of said strip means being pressed thereagainst in overlapping and surface contact relation due to the inherent resilient force of said strip means in said. second position of said first co-operable means, to thereby form a gas-tight seal in said flue.

4. Aflue sealing arrangement comprising an open frame for installation in a flue, a reciprocable curtain-type damper in said frame, a first co-operable imperforate wall means forming at least part of said damper, a second cooperable imperforate wall means forming part of said frame relative to which said first cooperable means is 5 movable, means operatively connected to said first cooperable means for reciprocably moving the latter relative to the opening of said frame, said second co-operable means terminating in a marginal edge, said first co-operable means being movable between a first position allowing free passage of 'flue gases through said open frame and a second position closing said passage through said frame, said second co-operable means having two inwardly convergent heat-resistant marginal spring strip means secured thereto and extending in planar form When not flexed at an acute angle to the plane of said first co-operable means, one on each side thereof, and engaging said marginal edge of said first co-operable means, said strip means terminating in at least one free edge projecting beyond said marginal edge onto the surface of said first cooper- References Cited in the file of this patent FOREIGN PATENTS 18,948 Austria Jan. 25, 1905 364,454 Germany Nov. 24, 1922 536,314 Great Britain May 9, 1941 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,996,063 August 15, 1961 Ernest Lowe It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent. should read as corrected below.

In the heading to the printed s pecification, between lines 5 and 6, insert the following:

Claims Priority, application Great Britain Aug. 1, 1956 Signed and sealed this 19th day of December 1961 (SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents USCOMM-DC- 

